3rd Generation Partnership Project-Long Term Evolution (3GPP LTE) standard group suggests that a base station (BS) and a mobile station (MS) can have different bandwidths therebetween and the communication must be possible in such an environment.
In order to allow an MS having a specific bandwidth to access a variety of BSs each having a different bandwidth, the MS must have a receiver structure supporting a scalable bandwidth. 3GPP LTE TR25.814 specifies that an MS can have a bandwidth of 10 MHz or higher, e.g., 15 MHz, 20 MHz, etc. and a BS has a bandwidth of 1.25 MHz, 2.5 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz. Further, 3GPP LTE TR25.814 specifies Inverse Fast Fourier Transform/Fast Fourier Transform (IFFT/FFT) size and sampling frequency.
In the resource allocation of shared control channel (SCH) and broadcast channel (BCH), the SCH and the BCH have a bandwidth of 1.25 MHz regardless of a total transmission bandwidth of a BS and are located at the center of the total transmission bandwidth. Regarding a BS with a transmission bandwidth of 5 MHz or higher, a method of allocating 5 MHz to the BCH is under discussion.
A conventional receiver is configured to receive a signal of a fixed bandwidth because a communication bandwidth between a BS and an MS is fixed.
FIG. 1 is a block diagram of a conventional zero-intermediate frequency (IF) receiver.
Referring to FIG. 1, the conventional zero-IF receiver includes a band-pass filter (BPF) 102, a mixer 103, a radio frequency (RF) local oscillator 104, a low-pass filter (LPF) 105, an automatic gain controller (AGC) 106, an analog-to-digital converter (ADC) 107, and a modem block 108. The BPF 102 filters an RF signal received through a receive (RX) antenna 101 with a bandwidth within which all frequency allocations (FAs) of a service provider can be accommodated. The RF local oscillator 104 oscillates an RF frequency to output an RF local oscillation frequency. The mixer 103 converts the RF signal from the BPF 102 into a baseband signal by using the RF local oscillation frequency output from the RF local oscillator 104. The LPF 105 filters the baseband signal from the mixer 103 with a fixed bandwidth of a corresponding FA. The AGC 106 controls magnitude or gain of the baseband signal output from the LPF 105. The ADC 107 converts the analog baseband signal output from the AGC 106 into a digital baseband signal. The modem block 108 demodulates the digital baseband signal output from the ADC 107.
The conventional receiver cannot support a scalable bandwidth because the communication bandwidth between the BS and the MS is fixed.
Hence, many attempts have been made to perform radio measurements on adjacent cells and receive broadcast system information in order for handover without interrupting data reception of a current home cell.